Auslegung: A journal of philosophy, volume 13, number 2 (summer, 1987) book review

Review of Irene E. Harvey's "Derrida and the Economy of Differance

Quantifying cognitive function in concussed athletes before and after acute exercise using a choice reaction time task

Following a concussion, cognitive deficits have been shown to last longer than symptom resolution. Currently clinicians rely heavily on symptom emergence following the fundamental exercises of the return to play (RTP) protocol, which may leave athletes at risk of returning to play too early if cognitive deficits have not been detected. The purpose of this study was to assess the effects of exercise on choice reaction time (CRT) both at rest and following an acute exercise in 3 populations: non-concussed (NC), recently concussed (RC), and post-concussion syndrome (PCS) individuals. A CRT task in the form of an iPad application measured each individual’s decision-making capabilities at four blocks: (1) 10 minutes prior to exercise, (2) Immediately prior to exercise, (3) immediately post exercise, and (4) 5 minutes post exercise. Participants were also fitted with an eye-tracking system during CRT task performance at rest in order to assess higher levels of cognitive processing. Results demonstrated a facilitative effect of learning and exercise arousal on CRT task performance in both NC and PCS but not in RC. Average RT in RC was not significantly different from NC while average RT in PCS was found to be significantly higher than NC. Gaze behaviour was significantly worse in PCS compared to NC while RC and NC were not significantly different. The absence of symptoms does not inherently mean that cognitive performance under acute physical stress has completely recovered in recently concussed individuals. On the other hand, PCS individuals continue to experience concussion-related symptoms, but appear to display partially recovered cognitive performance. Findings from the current study encourage the use of cognitive assessments following acute exercise during the RTP protocol in order to detect possibly lingering cognitive deficits

An athletic approach to studying perception-action integration: Does sport-specific training, and the impact of injury, influence how individuals visually guide navigation?

The objective of this thesis was to investigate perception-action integration capabilities of individuals during a choice navigation task. This task assessed navigation strategies in open space while individuals avoided colliding with two vertical obstacles that created a body-scaled, horizontal gap, at three varying obstacle distances from the starting location (3m, 5m, 7m). The two studies completed in this thesis employed the same paradigm to assess the hypothesized group differences. Gaze behaviours and kinematics of navigation strategies were compared between: 1) athletes specifically trained in navigating in open space versus non-athletes; and 2) athletes with post-concussion syndrome (PCS) versus non-concussed, specifically trained athletes. Specifically trained athletes have been identified as demonstrating more successful perception-action integration in discrete motor tasks related to their sport (Mann et al., 2007; Vickers, 2007). However, whether these abilities translate to the continuous motor task of obstacle avoidance in open space was unknown. The purpose of Study 1 was to identify the influence of sport-specific training on navigating in open space (i.e. navigational strategies of large field sport athletes) compared to age-matched, non-athletes. It was hypothesized that specifically-trained athletes would demonstrate fewer, longer fixations, suggesting a more successful perception-action integration strategy (as defined by Mann et al., 2007), and would employ more sport-specific navigation strategies than non-athletes by maintaining their straight trajectory toward the goal (Fajen & Warren, 2003). Athletes were found to make fewer, longer fixations than non-athletes. However, no differences were observed between navigation strategies of the two groups, nor were any kinematic measures found to differ between groups. It can be concluded that athletes and non-athletes differentially obtain visual information to perform the same actions, suggesting that athletes and non-athletes differentially perform perception-action integration when navigating in open space. Future studies are required to identify sport-specific nuances of navigation (moving obstacles, running) to better identify athletic-related navigation strategies. Although athletic training can enhance perception-action integration strategies, sport-related injuries can hinder this process. Following a concussion, individuals experience deficits of perception-action integration that persist well beyond 30 days of recovery, post-concussion (Baker and Cinelli, 2014; Slobounov et al., 2006). These perception-action integration deficits may also exist in individual with postconcussion syndrome (PCS). The purpose of the Study 2 was to identify whether perception-action integration deficits persist with the persistent physical symptoms of concussion characteristic of PCS. The current study revealed that athletes with PCS did not differ from non-concussed athletes on any measure of visual fixation strategy, nor were they found to differ on any kinematic measure assessed. These findings suggest that in the context of the current paradigm, athletes with PCS have no perception-action integration deficit. In that, athletes with PCS may have adapted perception-action integration strategies to navigate with equal efficiency as a specifically-trained group of athletes or that the paradigm was not sensitive enough to identify these differences. Such findings suggest that more research is required to assess what, if any, perception-action integration deficits persist with persisting physical symptoms of PCS to better benefit rehabilitative procedures and outcomes for these individuals. Together, these studies add to what was previously known about perception-action integration, as it relates to navigation. Both studies assessed perception-action integration in unique populations that add to understanding of behavioural dynamics in the sport setting. Study 1 builds on a line of research assessing affordance theory and behavioural dynamics in sport (Fajen, Riley, & Turvey, 2008). The findings of this study suggest that although navigation strategies did not differ between specifically trained athletes and non-athletes, visual search strategies employed in task did. Such findings add to the understanding that sport-specific training influences perception-action integration, through our understanding of how athletes obtain visual information to perform actions. This thesis did not identify perception-action integration deficits in athletes with PCS. These findings suggest that the individuals in the present study likely adapted to their injury as they demonstrated equal ability in gaze and navigation strategies to specifically-trained athletes. As such, further research is required to assess the cognitive, motor, and sensory-motor deficits that may persist with the persisting physical symptoms of PCS. As individuals with PCS do not demonstrate similar visuomotor integration deficits as individuals with acute concussions (Baker & Cinelli, 2014), such individuals must be assessed and researched as a separate population

Task-dependent Modulation of Cortical Excitability and Balance Control in Individuals with Post-concussion Syndrome

In most cases, symptoms resolve between 7-10 days post-concussion. However, in 10-15% of the concussed population, symptoms can remain unresolved for months to years following the head injury. The purpose of this thesis was two-fold, and was broken up into two studies, where the same individuals participated in both studies. The purpose of the first study was to quantify the differences in balance control between individuals with PCS (i.e., had been experiencing symptoms for \u3c30 days) and non-concussed individuals during a lower-limb reaching task. Participants completed a static balance assessment before and after a lower-limb reaching task, which incorporated a Go/No-Go paradigm. Results from this study revealed no differences in the static stability assessments, however, individuals with PCS demonstrated increased medial-lateral COP displacement as well as greater trunk pitch during the reaching task. Overall, the findings reveal persistent balance impairments in individuals with PCS, which may put this population at an increased risk of further injury. The purpose of the second study was to assess task-dependent modulation of cortical excitability prior to planned index finger abduction contractions comparing a non-concussed population to a population with PCS. The protocol in this study consisted of both single and paired-pulse transcranial magnetic stimulation (TMS) which was applied prior to the beginning of 3 different tasks (i.e., a rest condition with no plan to contract, a precision contraction, and a powerful contraction). In addition to the three tasks, participants also had to respond to a Go/No-Go cue. The results of this study revealed an increase in excitability prior to a precision contraction in both non-concussed and PCS groups. No differences in task-dependent modulation were found between the two groups with respect to intracortical facilitation and inhibition, however a negative correlation between number of symptoms reported (SCAT3 symptom evaluation) and intracortical facilitation was revealed. The increase in corticospinal excitability prior to a precision contraction was not explained by the two cortical mechanisms we assessed and may therefore be due to spinal modulation or a different cortical mechanism. Overall, based on the results from this thesis, it appears that individuals with PCS have balance impairments, which may be a result of an inability to maximally activate their postural muscles. Furthermore, it appears that those individuals who reported a higher number of symptoms had greater reductions in intracortical facilitation, likely reflecting the heterogeneity of this clinical group

An Integrated Coastal Sediment Management Plan: The Example of the Tuscany Region (Italy)

This paper presents the results of a study carried out to support the Region of Tuscany Coastal Sediment Management Plan, with the main aim of establishing the sediment budget considering the time span from 1981-1985 to 2005 for the 56 coastal sectors into which the 215 km-long continental sandy coast of Tuscany (Italy) was divided. The sand stability (according to a stability index) and colour compatibility (according to the CIEL*a*b* colour space with an acceptability range conforming to national guidelines) were determined in order to assess the possibility of using the available sediment in accreting sectors to nourish the beach in eroding areas. Only in two cases-i.e., the updrift of a harbour (at Viareggio) and in a convergence zone (at Marina di Pietrasanta)-are the volumes of sufficient magnitude to support a large nourishment project; however, the mean sand size is too small to guarantee efficient nourishment, even with medium-term stability. In contrast, the colour difference, in most of the cases, was shown to be acceptable. Other small sediment stocks, suitable for colour but not for grain size, can be used for periodic ephemeral nourishment works to support seasonal tourist activities. The limited resources available make it necessary to adopt a plan for their optimal use from a regional perspective. This kind of study is of great interest for the proposal of sound management actions to counteract the increasing erosion processes linked to climate change phenomena and human effects on rivers and coastal systems

Polyhydroxyalkanoate (PHA): Review of synthesis, characteristics, processing and potential applications in packaging

Polyhydroxyalkanoates (PHAs) are gaining increasing attention in the biodegradable polymer market due to their promising properties such as high biodegradability in different environments, not just in composting plants, and processing versatility. Indeed among biopolymers, these biogenic polyesters represent a potential sustainable replacement for fossil fuel-based thermoplastics. Most commercially available PHAs are obtained with pure microbial cultures grown on renewable feedstocks (i.e. glucose) under sterile conditions but recent research studies focus on the use of wastes as growth media. PHA can be extracted from the bacteria cell and then formulated and processed by extrusion for production of rigid and flexible plastic suitable not just for the most assessed medical applications but also considered for applications including packaging, moulded goods, paper coatings, non-woven fabrics, adhesives, films and performance additives. The present paper reviews the different classes of PHAs, their main properties, processing aspects, commercially available ones, as well as limitations and related improvements being researched, with specific focus on potential applications of PHAs in packaging

Recursive patterns in online echo chambers

Despite their entertainment oriented purpose, social media changed the way users access information, debate, and form their opinions. Recent studies, indeed, showed that users online tend to promote their favored narratives and thus to form polarized groups around a common system of beliefs. Confirmation bias helps to account for users’ decisions about whether to spread content, thus creating informational cascades within identifiable communities. At the same time, aggregation of favored information within those communities reinforces selective exposure and group polarization. Along this path, through a thorough quantitative analysis we approach connectivity patterns of 1.2 M Facebook users engaged with two very conflicting narratives: scientific and conspiracy news. Analyzing such data, we quantitatively investigate the effect of two mechanisms (namely challenge avoidance and reinforcement seeking) behind confirmation bias, one of the major drivers of human behavior in social media. We find that challenge avoidance mechanism triggers the emergence of two distinct and polarized groups of users (i.e., echo chambers) who also tend to be surrounded by friends having similar systems of beliefs. Through a network based approach, we show how the reinforcement seeking mechanism limits the influence of neighbors and primarily drives the selection and diffusion of contents even among like-minded users, thus fostering the formation of highly polarized sub-clusters within the same echo chamber. Finally, we show that polarized users reinforce their preexisting beliefs by leveraging the activity of their like-minded neighbors, and this trend grows with the user engagement suggesting how peer influence acts as a support for reinforcement seeking

Heat-Wave Events in Spain: Air Mass Analysis and Impacts on 7

The present paper describes and characterizes the air mass circulation during the heat-wave events registered during the period 2005-2014 over Spain, paying special attention on the role of the Saharan circulations. With this purpose, backward trajectories at 500, 1500 and 3000 m in Seville (south), Madrid (centre) and Bilbao (north) during the thirteen heat-wave events identified during this period are analysed. Finally, the impact of the heat-wave events and of each advection pattern on 7Be activity concentrations is also analysed. The air mass results indicate that the heat-wave events are characterized roughly by western, southern and nearby advections, with a higher frequency of the first two types. The analysis shows a general and large impact at lower levels of westerly flows and an increase of African air masses with height. The Saharan air masses present a different spatial impact over Spain, with a decreasing occurrence and a decrease in the simultaneous occurrence percentage from south to north. The 7Be activity concentrations during these events show an increase of concentrations in central and southern areas and a small decrease in northern Spain. This increase is not associated with Saharan air masses, but instead to the arrival of distant westerly air masses.JRC.G.II.7-Nuclear securit